Argenx SE (NASDAQ:ARGX) stock jumped about 12% in Monday’s premarket trading after the company reported positive topline results from its Phase 3 ALKIVIA study.
The trial evaluated VYVGART Hytrulo, or efgartigimod alfa and hyaluronidase-qvfc, in adults with autoimmune myositis.
Meeting the Primary Endpoint
The study successfully achieved its primary endpoint (p=0.0011).
In a combined population of patients with immune-mediated necrotizing myopathy (IMNM) and dermatomyositis (DM), efgartigimod showed a statistically significant and clinically meaningful 15.4-point greater improvement in the mean Total Improvement Score (TIS) at Week 52 compared to the placebo group (47.95 vs 32.56).
Rapid and Sustained Benefits
Patients receiving efgartigimod in the combined population consistently exhibited improvements over the placebo starting as early as Week 4. These improvements were statistically significant and sustained throughout the entire year of treatment, even with steroid tapering.
Consistent Clinical Improvement
Prespecified subtype analyses revealed that the primary endpoint of Mean TIS at 52 weeks was also met in IMNM patients treated with efgartigimod (p=0.0048), demonstrating a 14.8-point greater improvement over the placebo (45.05 vs 30.24).
A similar clinically meaningful improvement of 14.5 points (p=0.1093) was observed in DM patients (51.51 vs 36.96), although statistical significance was not reached in this smaller group.
Impact on Muscle and Skin Measures
In both IMNM and DM, all six core set measures of TIS contributed to the treatment effect, each favoring efgartigimod over the placebo.
These measures span muscle strength, everyday physical function, and disease activity beyond the muscle. Additionally, an improvement in skin disease activity was observed in DM patients.
Well-Tolerated with Consistent Safety Profile
Efgartigimod was well-tolerated by patients in the ALKIVIA study, with a safety profile consistent with previous studies. Detailed results from the study will be presented at an upcoming medical meeting.
Efgartigimod is also being evaluated as a potential treatment for other autoimmune rheumatologic diseases, such as Sjögren’s disease and systemic sclerosis.
William Blair expects commercialization in IMNM by the end of 2027 and projects peak sales of $3 billion. The firm noted that management estimates about 20,000 IMNM patients in the U.S., where no therapies are currently approved. It added that an approved treatment could also drive higher diagnosis rates, similar to the CIDP market.
Analyst Matt Phipps assumes peak sales of $1.7 billion in DM. He cited greater competition in the indication and remaining questions about the magnitude of the benefit.
“While the exact timing of commercialization in DM remains a question, we believe the consistent level of efficacy on TIS will slightly increase investor confidence in the blockbuster opportunity in DM as well,” Phipps said in an investor note Monday.
ARGX Stock Price Activity: Argenx shares were up 11.94% at $952.93 during premarket trading on Monday, according to Benzinga Pro data.
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